It is usual when designing an air conditioner system to position the air outlets above the occupied space in any room, that is to say above head height. There is then no risk of creating unpleasant draughts and the incoming air is able to mix with ambient air before entering the region of the room which is occupied. In certain buildings, this is not possible and the air conditioner ducts and outlets must be floor mounted. The usually cool air then enters the occupied space directly from the outlets and there are unpleasant draught sensations and also wide variations in temperature between, for example, floor level and head height.